Star-forming Galaxies in the Distant Universe with Herschel and LOFAR

Lead Research Organisation: University of Sussex
Department Name: Sch of Mathematical & Physical Sciences

Abstract

A key goal in astrophysics is to understand galaxy formation and evolution. Galaxies today have built up their stellar populations by star-formation and merging. Therefore direct measurements of the star-formation rates in galaxies at high redshift are a key component in advancing our theoretical understanding of those processes. However, at high redshift at least half of the star formation activity is obscured by dust and can only be probed by observations at far infrared (FIR) and radio wavelengths. Such observations are particularly critical for galaxy evolution scenarios. This was notably demonstrated in recent years by the famous discovery by the far infrared instrument SCUBA (and subsequent radio observations) of numerous galaxies with very high star-formation rates that are extremely hard to explain by current models. LOFAR and ESA's Herschel mission were designed for studying these obscured star-forming galaxies at high redshift and high profile survey projects are being carried out by both facilities. The pioneering results from surveys with SCUBA are based on few galaxies over areas of 0.25 sq. degrees. In contrast the Herschel Extragalactic Legacy Project collates date over 1300 deg^2 degrees detecting 100k far infrared galaxies and the LOFAR Deep survey will cover similar areas. These areas are necessary to cover the full range of galaxy environments (from clusters to voids) and to provide statistically significant samples to rigorously test galaxy formation theories. These two surveys are closely coordinated in the same regions of the sky since both probe obscured star-formation but through different mechanisms. At Sussex we are developing new Bayesian tools (XID+) to empirically model galaxy survey data. In addition there will be a new survey project LOFAR WEAVE which uses WHT to get redshifts for LOFAR sources.
The objective of the studentship will be (a) to provide LOFAR identifications for the most extreme sub-mm sources, which are candidates for the theory-busting highest redshift and high star-formation rate galaxies (b) to exploit XID+ test for evolution in the well-known FIR/radio correlation (c) to extend XID+ to work with the spectral data from LOFAR WEAVE and determine definitive star formation rate calibration relations and prepare for larger spectroscopic surveys in the future such as 4MOST.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
ST/R505146/1 01/10/2017 30/09/2021
1950620 Studentship ST/R505146/1 21/09/2017 30/09/2021 Ian McCheyne
 
Description Deblended FIR fluxes for LOFAR optical counterparts and their far infrared radio correlation 
Organisation LOFAR
Country Netherlands 
Sector Academic/University 
PI Contribution I have added deblended far infrared fluxes to the optical counterparts of the LOTSS deep fields. This has been done using the software XID+, developed at Sussex University as part of the Hercshel Extragalatic Legacy Project. I have also measured the far infrared radio correlation using this deep data at 150MHz. I was also part of the team that did the crossmatching between the radio and optical catalogues
Collaborator Contribution The LOTSS survey team have provided the radio images and catalogues and well as new optical catalogues in the deep fields. They have also provided the crossmatching between the radio and optical catalogues.
Impact As of writing this there have been no public outcomes. But the aim is to have done a public release of all the deep fields data within the next few months and to have a special issue in Astronomy and Astrophysics and the same time.
Start Year 2018